Promise Pegasus2 4tb Drive 5900 / 7200

Looking for Total Cost of ownership and noticed that the 4tb Promise hot swaps are listed as 7200 whilst the small detail says the 32TB R8 System uses 5900 4TB hot swaps. Is this the right product for the R8 32TB or is there a different SKU. Also would like to know length of the Thunderbolt that comes with the device 2m, 3m, 0.5m No info on this. Revolutionary design of the new Mac Pro means I would want to have it on the desktop (also very quiet). Or if its cold, might mount it under my swivel chair to keep my bum warm.